Method for synthesis of monocyclopentadienyl complexes of zirconium and hafnium

ABSTRACT

Catalyst systems and methods for making and using the same are disclosed. In an example, a method of synthesizing a monocyclopentadienyl compound is provided. The method includes melting a dicyclopentadienyl compound including the following structure: 
     
       
         
         
             
             
         
       
     
     As used herein, M is hafnium or zirconium. Each R is independently an H, a hydrocarbyl group, a substituted hydrocarbyl group, a heteroatom group. Each X is a leaving group selected from a halogen or a heteroatom group. A reaction melt is formed by adding a metal salt including the following structure: 
     
       
         
         
             
             
         
       
     
     A monocyclopentadienyl compound is deposited from a vapor formed over the reaction melt, wherein the monocyclopentadienyl compound includes the following structure:

BACKGROUND

Ethylene alpha-olefin (polyethylene) copolymers are typically producedin a low pressure reactor, utilizing, for example, solution, slurry, orgas phase polymerization processes. Polymerization takes place in thepresence of catalyst systems such as those employing, for example, aZiegler-Natta catalyst, a chromium based catalyst, a metallocenecatalyst, or combinations thereof.

A number of catalyst compositions containing single site, e.g.,metallocene, catalysts have been used to prepare polyethylenecopolymers, producing relatively homogeneous copolymers at goodpolymerization rates. In contrast to traditional Ziegler-Natta catalystcompositions, single site catalyst compositions, such as metallocenecatalysts, are catalytic compounds in which each catalyst moleculecontains one or only a few polymerization sites. Single site catalystsoften produce polyethylene copolymers that have a narrow molecularweight distribution. Control of the molecular weight distribution andother properties can be achieved through various techniques, such asusing mixed ligand metallocenes.

Monocyclopentadienyl complexes of zirconium and hafnium are precursorsto mixed ligand bis(cyclopentadienyl) metal complexes (mixed ligandmetallocenes), such as (n-propylcyclopentadienyl)(tetramethylcyclopentadienyl) zirconiumdichloride (hereinafter catalystA), among others.

There are several known routes to monocyclopentadienyl complexes ofzirconium and hafnium. Monocyclopentadienyl complexes of zirconium andhafnium with bulky cyclopentadienyl substituents such a tetramethyl orpentamethylcyclopentadiene are relatively easy to prepare. For example,pentamethylcyclopentadienylzirconiumtrichloride can be prepared frompentamethylcyclopentadienyllithium and ZrCl₄ in ether.

Further, catalyst A can be made via the reaction of (tetramethyl)(trimethylsilyl) cyclopentadiene with ZrCl₄ at high temperature (80-90°C.) in toluene. The product precipitates out of solution and afterisolation is ready for further conversion to A by treatment withn-propylcyclopentadienyllithium as shown in the following reactionscheme:

As will be discussed in more detail below, the initially formed(tetramethylcyclopentadienyl)zirconiumtrichloride is stable under theseconditions and does not disproportionate to an appreciable extent as domonocyclopentadienyl complexes of zirconium and hafnium with less bulkygroups such as n-propylcyclopentadienyl.

An alternative synthesis of monocyclopentadienyl complexes of zirconiumand hafnium has been reported by Lund and Livinghouse in Organometallics(1990), 9(9), 2426-7. In these methods either bis(dimethylsulfide)ZrCl₄or bis(dimethylsulfide)HfCl₄ are reacted withtrimethylsilylcyclopentediene and tri-n-butyltincyclopentadienerespectively at low temperature to form the monocyclopentadienylcomplexes as shown in the following reaction scheme:

Monocyclopentadienyl complexes of zirconium and hafnium can also beformed via the reaction of metallocenes with the respective metaltetrahalide. This is especially convenient when the starting bis complexis commercially available or easily synthesized.

US2007/0060722 discloses a method for making (n-BuCp)ZrCl₃ frombis(n-butylcyclopentadienyl)zirconiumdichloride andzirconiumtetrachloride in which the two reactants are refuxed for 20hours in toluene, the reaction mixture is centrifuged to remove ZrCl₄,and the resulting product is purified by multiple precipitations fromCH₂Cl₂/pentane to yield the product in about 87% yield. The purity ofthe material is reported to have a mono to bis ratio of 52:1 as comparedwith the same reaction carried out at room temperature for 20 h whichgave a mono to bis ratio of 1.4 to 1. There is also an example in which(1,3-butyl-methylcyclopentadienyl)zirconium trichloride is prepared inthe same manner frombis(1,3-butyl-methylcyclopentadienyl)zirconiumdichloride (E dichloride)and ZrCl₄ in 76% yield.

The procedures detailed above may provide a monocyclopentadienylcomplex, but take significant time for completion. Further, in many ofthese techniques only bulky substituents on the cyclopentadiene ringslow or prevent disproportionation to a dicyclopentadienyl complex.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a drawing of a structure for (n-propylcyclopentadienyl)zirconiumtrichloride.

FIG. 2 is an NMR spectrum of(n-propylcyclopentadienyl)zirconiumtrichloride (dimethoxyethane).

FIG. 3 is an NMR spectrum of (n-propylcyclopentadienyl)(1-methylindenyl)zirconiumdichloride.

FIG. 4 is an NMR spectrum of (1,3-butyl-methyl-cyclopentadienyl)zirconiumtrichloride(dimethoxyethane).

FIG. 5 is an NMR spectrum of (n-Propylcyclopentadienyl)hafniumtrichloride (dimethoxyethane).

FIG. 6 is an NMR spectrum of the mixed ligand compound(nPrCp)(P,O)ZrBz₂.

FIG. 7 is a drawing of a structure for a mixed ligand structure forusing the mono-cyclopentadienyl complexes formed using the currenttechniques.

SUMMARY

An example described herein provides a method of synthesizing a catalystcompound is provided. The method includes melting a dicyclopentadienylcompound including the following structure:

As used herein, M is hafnium or zirconium. Each R is independently an H,a hydrocarbyl group, a substituted hydrocarbyl group, a heteroatomgroup. Each X is a leaving group selected from a halogen or a heteroatomgroup. A reaction melt is formed by adding a metal salt including thefollowing structure:

A monocyclopentadienyl compound is deposited from a vapor formed overthe reaction melt, wherein the monocyclopentadienyl compound includesthe following structure:

The monocyclopentadienyl compound is reacted with a ligand precursor toform the catalyst compound.

Another example described herein provides a method of forming apolyethylene copolymer. The method includes reacting ethylene and aC₄-C₂₀ alpha-olefin with a polymerization catalyst, wherein thepolymerization catalyst is formed by synthesizing a monocyclopentadienylcompound by melting a dicyclopentadienyl compound including thefollowing structure:

As used herein, M is hafnium or zirconium. Each R is independently an H,a hydrocarbyl group, a substituted hydrocarbyl group, a heteroatomgroup. Each X is a leaving group selected from a halogen or a heteroatomgroup. A reaction melt is formed by adding a metal salt including thefollowing structure:

A monocyclopentadienyl compound is deposited from a vapor formed overthe reaction melt, wherein the monocyclopentadienyl compound includesthe following structure:

The monocyclopentadienyl compound is reacted with a ligand precursor toform the catalyst compound. The catalyst compound is supported to formthe polymerization catalyst.

Another example described herein provides a method of forming amonocyclopentadienyl complex of hafnium or zirconium. The methodincludes melting a dicyclopentadienyl compound including the followingstructure:

As used herein, M is hafnium or zirconium. Each R is independently an H,a hydrocarbyl group, a substituted hydrocarbyl group, a heteroatomgroup. Each X is a leaving group selected from a halogen or a heteroatomgroup. A reaction melt is formed by adding a metal salt including thefollowing structure:

A monocyclopentadienyl compound is deposited from a vapor formed overthe reaction melt, wherein the monocyclopentadienyl compound includesthe following structure:

DETAILED DESCRIPTION

Examples described herein provide a method for forming amonocyclopentadienyl species. The method include reacting abis(cyclopentadienyl)zirconium or hafnium species with ZrCl₄ or HfCl₄,wherein the reaction is driven to completion via sublimation ordistillation of the product monocyclopentadienyl species out of thereaction mixture. As an example, the reaction procedure takes advantageof the equilibrium shown in equation 1:

In equation 1, M can be either zirconium (Zr) or hafnium (Hf). Theequilibrium constant, K_(eq), depends on the metal (Zr vs Hf) and thesteric hindrance or size of cyclopentadienyl ligand. The equilibrium maylie farther to the right for Hf than for Zr and it may also lie fartherto the right the larger the cyclopentadienyl ligand. The reactants, R1and R2, are melted together in an inert atmosphere to form a reactionmelt. The product (P) forms in the reaction melt and is sublimed ordistilled from the reaction melt, driving the reaction to the right. Theproduct is then deposited in a cooler region of an apparatus. Thesublimed or distilled product typically has a purity of >95% and can bepurified further, for example, by precipitation as the DME adduct intoluene.

The technique may be used in commercial processes to form the productcontinuously. This would be performed by continuously adding thedicyclopentadienyl compound and the metal salt to the reaction melt,while continuously depositing the monocyclopentadienyl compound from thevapor.

Catalyst Compounds

Metallocene Catalyst Compounds

Metallocene catalyst compounds can include “half sandwich” and/or “fullsandwich” compounds having one or more Cp ligands (cyclopentadienyl andligands isolobal to cyclopentadienyl) bound to at least one Group 3 toGroup 12 metal atom, and one or more leaving groups bound to the atleast one metal atom. As used herein, all reference to the PeriodicTable of the Elements and groups thereof is to the NEW NOTATIONpublished in HAWLEY'S CONDENSED CHEMICAL DICTIONARY, Thirteenth Edition,John Wiley & Sons, Inc., (1997) (reproduced there with permission fromIUPAC), unless reference is made to the Previous IUPAC form noted withRoman numerals (also appearing in the same), or unless otherwise noted.

The Cp ligands are one or more rings or ring systems, at least a portionof which includes π-bonded systems, such as cycloalkadienyl ligands andheterocyclic analogues. The rings or ring systems typically includeatoms selected from the group consisting of Groups 13 to 16 atoms, and,in a particular example, the atoms that make up the Cp ligands areselected from the group consisting of carbon, nitrogen, oxygen, silicon,sulfur, phosphorous, germanium, boron, aluminum, and combinationsthereof, where carbon makes up at least 50% of the ring members. In amore particular example, the Cp ligands are selected from the groupconsisting of substituted and unsubstituted cyclopentadienyl ligands andligands isolobal to cyclopentadienyl, non-limiting examples of whichinclude cyclopentadienyl, indenyl, fluorenyl and other structures.Further non-limiting examples of such ligands include cyclopentadienyl,cyclopentaphenanthreneyl, indenyl, benzindenyl, fluorenyl,octahydrofluorenyl, cyclooctatetraenyl, cyclopentacyclododecene,phenanthrindenyl, 3,4-benzofluorenyl, 9-phenylfluorenyl,8-H-cyclopent[a]acenaphthylenyl, 7-H-dibenzofluorenyl,indeno[1,2-9]anthrene, thiophenoindenyl, thiophenofluorenyl,hydrogenated versions thereof (e.g., 4,5,6,7-tetrahydroindenyl, or “H₄Ind”), substituted versions thereof (as discussed and described in moredetail below), and heterocyclic versions thereof.

The metal atom “M” of the metallocene catalyst compound can be selectedfrom the group consisting of Groups 3 through 12 atoms and lanthanideGroup atoms in one example; and selected from the group consisting ofGroups 3 through 10 atoms in a more particular example, and selectedfrom the group consisting of Sc, Ti, Zr, Hf, V, Nb, Ta, Mn, Re, Fe, Ru,Os, Co, Rh, Ir, and Ni in a more particular example; and selected fromthe group consisting of Groups 4, 5, and 6 atoms in a more particularexample, and Ti, Zr, Hf atoms in a more particular example, and Hf in amore particular example. The oxidation state of the metal atom “M” canrange from 0 to +7 in one example; and in a more particular example, canbe +1, +2, +3, +4, or +5; and in a more particular example can be +2, +3or +4. The groups bound to the metal atom “M” are such that thecompounds described below in the formulas and structures areelectrically neutral, unless otherwise indicated. The Cp ligand forms atleast one chemical bond with the metal atom M to form the “metallocenecatalyst compound.” The Cp ligands are distinct from the leaving groupsbound to the catalyst compound in that they are not highly susceptibleto substitution/abstraction reactions.

The one or more metallocene catalyst compounds can be represented by theformula (I):

Cp^(A)Cp^(B)MX_(n)   (I)

in which M is as described above; each X is chemically bonded to M; eachCp group is chemically bonded to M; and n is 0 or an integer from 1 to4, and either 1 or 2 in a particular example.

The ligands represented by Cp^(A) and Cp^(B) in formula (I) can be thesame or different cyclopentadienyl ligands or ligands isolobal tocyclopentadienyl, either or both of which can contain heteroatoms andeither or both of which can be substituted by a group R. In at least onespecific example, Cp^(A) and Cp^(B) are independently selected from thegroup consisting of cyclopentadienyl, indenyl, tetrahydroindenyl,fluorenyl, and substituted derivatives of each.

Independently, each Cp^(A) and Cp^(B) of formula (I) can beunsubstituted or substituted with any one or combination of substituentgroups R. Non-limiting examples of substituent groups R as used instructure (I) as well as ring substituents in structures Va-d, discussedand described below, include groups selected from the group consistingof hydrogen radicals, alkyls, alkenyls, alkynyls, cycloalkyls, aryls,acyls, aroyls, alkoxys, aryloxys, alkylthiols, dialkylamines,alkylamidos, alkoxycarbonyls, aryloxycarbonyls, carbamoyls, alkyl- anddialkyl-carbamoyls, acyloxys, acylaminos, aroylaminos, and combinationsthereof. More particular non-limiting examples of alkyl substituents Rassociated with formulas (I) through (Va-d) include methyl, ethyl,propyl, butyl, pentyl, hexyl, cyclopentyl, cyclohexyl, benzyl, phenyl,methylphenyl, and tert-butylphenyl groups and the like, including alltheir isomers, for example, tertiary-butyl, isopropyl, and the like.Other possible radicals include substituted alkyls and aryls such as,for example, fluoromethyl, fluroethyl, difluroethyl, iodopropyl,bromohexyl, chlorobenzyl, hydrocarbyl substituted organometalloidradicals including trimethylsilyl, trimethylgermyl, methyldiethylsilyl,and the like, and halocarbyl-substituted organometalloid radicals,including tris(trifluoromethyl)silyl, methylbis(difluoromethyl)silyl,bromomethyldimethylgermyl and the like; and disubstituted boron radicalsincluding dimethylboron, for example; and disubstituted Group 15radicals including dimethylamine, dimethylphosphine, diphenylamine,methylphenylphosphine, as well as Group 16 radicals including methoxy,ethoxy, propoxy, phenoxy, methylsulfide, and ethylsulfide. Othersubstituent groups R include, but are not limited to, olefins such asolefinically unsaturated substituents including vinyl-terminated ligandssuch as, for example, 3-butenyl, 2-propenyl, 5-hexenyl, and the like. Inone example, at least two R groups (two adjacent R groups in aparticular example) are joined to form a ring structure having from 3 to30 atoms selected from the group consisting of carbon, nitrogen, oxygen,phosphorous, silicon, germanium, aluminum, boron, and combinationsthereof. Also, a substituent group R such as 1-butanyl can form abonding association to the element M.

Each X in the formula (I) above and for the formulas, or structures,(II) through (Va-d) below is independently selected from the groupconsisting of: any leaving group, in one example; halogen ions,hydrides, C₁ to C₁₂ alkyls, C₂ to C₁₂ alkenyls, C₆ to C₁₂ aryls, C₇ toC₂₀ alkylaryls, C₁ to C₁₂ alkoxys, C₆ to C₁₆ aryloxys, C₇ to C₈alkylaryloxys, C₁ to C₁₂ fluoroalkyls, C₆ to C₁₂ fluoroaryls, and C₁ toC₁₂ heteroatom-containing hydrocarbons and substituted derivativesthereof, in a more particular example; hydride, halogen ions, C₁ to C₆alkyls, C₂ to C₆ alkenyls, C₇ to C₁₈ alkylaryls, C₁ to C₆ alkoxys, C₆ toC₁₄ aryloxys, C₇ to C₁₆ alkylaryloxys, C₁ to C₆ alkylcarboxylates, C₁ toC₆ fluorinated alkylcarboxylates, C₆ to C₁₂ arylcarboxylates, C₇ to C₁₈alkylarylcarboxylates, C₁ to C₆ fluoroalkyls, C₂ to C₆ fluoroalkenyls,and C₇ to C₁₈ fluoroalkylaryls in a more particular example; hydride,chloride, fluoride, methyl, phenyl, phenoxy, benzoxy, tosyl,fluoromethyls and fluorophenyls, in a more particular example; C₁ to C₁₂alkyls, C₂ to C₁₂ alkenyls, C₆ to C₁₂ aryls, C₇ to C₂₀ alkylaryls,substituted C₁ to C₁₂ alkyls, substituted C₆ to C₁₂ aryls, substitutedC₇ to C₂₀ alkylaryls and C₁ to C₁₂ heteroatom-containing alkyls, C₁ toC₁₂ heteroatom-containing aryls, and C₁ to C₁₂ heteroatom-containingalkylaryls, in a more particular example; chloride, fluoride, C₁ to C₆alkyls, C₂ to C₆ alkenyls, C₇ to C₁₈ alkylaryls, halogenated C₁ to C₆alkyls, halogenated C₂ to C₆ alkenyls, and halogenated C₇ to C₁₈alkylaryls, in a more particular example; fluoride, methyl, ethyl,propyl, phenyl, methylphenyl, dimethylphenyl, trimethylphenyl,fluoromethyls (mono-, di- and trifluoromethyls) and fluorophenyls(mono-, di-, tri-, tetra- and pentafluorophenyls), in a more particularexample; and fluoride, in a more particular example.

Other non-limiting examples of X groups include amines, phosphines,ethers, carboxylates, dienes, hydrocarbon radicals having from 1 to 20carbon atoms, fluorinated hydrocarbon radicals (e.g., —C₆F₅(pentafluorophenyl)), fluorinated alkylcarboxylates (e.g., CF₃C(O)O⁻),hydrides, halogen ions and combinations thereof. Other examples of Xligands include alkyl groups such as cyclobutyl, cyclohexyl, methyl,heptyl, tolyl, trifluoromethyl, tetramethylene, pentamethylene,methylidene, methyoxy, ethyoxy, propoxy, phenoxy, bis(N-methylanilide),dimethylamide, dimethylphosphide radicals and the like. In one example,two or more Xs form a part of a fused ring or ring system. In at leastone specific example, X can be a leaving group selected from the groupconsisting of chloride ions, bromide ions, C₁ to C₁₀ alkyls, and C₂ toC₁₂ alkenyls, carboxylates, acetylacetonates, and alkoxides.

The catalyst system can include other single site catalysts such asGroup 15-containing catalysts. The catalyst system can include one ormore second catalysts in addition to the single site catalyst compoundsuch as chromium-based catalysts, Ziegler-Natta catalysts, one or moreadditional single-site catalysts such as metallocenes or Group15-containing catalysts, bimetallic catalysts, and mixed catalysts. Thecatalyst system can also include AlCl₃, cobalt, iron, palladium, or anycombination thereof.

Catalyst Slurry

The catalyst system may include a catalyst or catalyst component in aslurry, which may have a single catalyst compound, or may have addedcatalyst components that are added as a solution to the slurry orcosupported on the support. Any number of combinations of catalystcomponents may be used in examples. For example, the catalyst componentslurry can include an activator and a support, or a supported activator.Further, the slurry can include a catalyst compound in addition to theactivator and the support. As noted, the catalyst compound in the slurrymay be supported.

The slurry may include one or more activators and supports, and one morecatalyst compounds. For example, the slurry may include two or moreactivators (such as alumoxane and a modified alumoxane) and a catalystcompound, or the slurry may include a supported activator and more thanone catalyst compounds. In one example, the slurry includes a support,an activator, and a catalyst compound. In another example the slurryincludes a support, an activator and two different catalyst compounds,which may be added to the slurry separately or in combination. Theslurry, containing silica and alumoxane, may be contacted with acatalyst compound, allowed to react, and thereafter the slurry iscontacted with another catalyst compound, for example, in a trim system.

The molar ratio of metal in the activator to metal, such as aluminum, ormetalloid, such as boron,in the catalyst compound in the slurry may be1000:1 to 0.5:1, 300:1 to 1:1, or 150:1 to 1:1. The slurry can include asupport material which may be any inert particulate carrier materialknown in the art, including, but not limited to, silica, fumed silica,alumina, clay, talc or other support materials such as disclosed above.In one example, the slurry contains silica and an activator, such asmethyl aluminoxane (“MAO”), modified methyl aluminoxane (“MMAO”), asdiscussed further below.

One or more diluents or carriers can be used to facilitate thecombination of any two or more components of the catalyst system in theslurry or in the trim catalyst solution. For example, the single sitecatalyst compound and the activator can be combined together in thepresence of toluene or another non-reactive hydrocarbon or hydrocarbonmixture to provide the catalyst mixture. In addition to toluene, othersuitable diluents can include, but are not limited to, ethylbenzene,xylene, pentane, hexane, heptane, octane, other hydrocarbons, or anycombination thereof. The support, either dry or mixed with toluene canthen be added to the catalyst mixture or the catalyst/activator mixturecan be added to the support.

Catalyst Supports

As used herein, the terms “support” and “carrier” are usedinterchangeably and refer to any support material, including a poroussupport material, such as talc, inorganic oxides, and inorganicchlorides. The one or more single site catalyst compounds of the slurrycan be supported on the same or separate supports together with theactivator, or the activator can be used in an unsupported form, or canbe deposited on a support different from the single site catalystcompounds, or any combination thereof. This may be accomplished by anytechnique commonly used in the art. There are various other methods inthe art for supporting a single site catalyst compound. For example, thesingle site catalyst compound can contain a polymer bound ligand. Thesingle site catalyst compounds of the slurry can be spray dried. Thesupport used with the single site catalyst compound can befunctionalized.

The support can be or include one or more inorganic oxides, for example,of Group 2, 3, 4, 5, 13, or 14 elements. The inorganic oxide caninclude, but is not limited to silica, alumina, titania, zirconia,boria, zinc oxide, magnesia, or any combination thereof. Illustrativecombinations of inorganic oxides can include, but are not limited to,alumina-silica, silica-titania, alumina-silica-titania,alumina-zirconia, alumina-titania, and the like. The support can be orinclude alumina, silica, or a combination thereof. In one exampledescribed herein, the support is silica.

Suitable commercially available silica supports can include, but are notlimited to, ES757, ES70, and ES7OW available from PQ Corporation.Suitable commercially available silica-alumina supports can include, butare not limited to, SIRAL® 1, SIRAL® 5, SIRAL® 10, SIRAL® 20, SIRAL®28M, SIRAL® 30, and SIRAL® 40, available from SASOL®. Generally,catalysts supports comprising silica gels with activators, such asmethylaluminoxanes (MAOs), are used in the trim systems described, sincethese supports may function better for co-supporting solution carriedcatalysts. Suitable supports may also be selected from the Cab-o-sil®materials available from Cabot Corporation and silica materialsavailable from the Grace division of W.R. Grace & Company.

Catalyst supports may also include polymers that are covalently bondedto a ligand on the catalyst. For example, two or more catalyst moleculesmay be bonded to a single polyolefin chain.

Catalyst Activators

As used herein, the term “activator” may refer to any compound orcombination of compounds, supported, or unsupported, which can activatea single site catalyst compound or component, such as by creating acationic species of the catalyst component. For example, this caninclude the abstraction of at least one leaving group (the “X” group inthe single site catalyst compounds described herein) from the metalcenter of the single site catalyst compound or component. The activatormay also be referred to as a “co-catalyst”.

For example, the activator can include a Lewis acid or anon-coordinating ionic activator or ionizing activator, or any othercompound including Lewis bases, aluminum alkyls, and/orconventional-type co-catalysts. In addition to methylaluminoxane (“MAO”)and modified methylaluminoxane (“MMAO”) mentioned above, illustrativeactivators can include, but are not limited to, aluminoxane or modifiedaluminoxane, and/or ionizing compounds, neutral or ionic, such asDimethylanilinium tetrakis(pentafluorophenyl)borate, Triphenylcarbeniumtetrakis(pentafluorophenyl)borate, Dimethylaniliniumtetrakis(3,5-(CF₃)₂phenyl)borate, Triphenylcarbeniumtetrakis(3,5-(CF₃)₂phenyOborate, Dimethylaniliniumtetrakis(perfluoronapthyl)borate, Triphenylcarbeniumtetrakis(perfluoronapthyl)borate, Dimethylaniliniumtetrakis(pentafluorophenyl)aluminate, Triphenylcarbeniumtetrakis(pentafluorophenyl)aluminate, Dimethylaniliniumtetrakis(perfluoronapthyl)aluminate, Triphenylcarbeniumtetrakis(perfluoronapthyl)aluminate, a tris(perfluorophenyl)boron, atris(perfluoronaphthyl)boron, t ris(perfluorophenyl)aluminum, atris(perfluoronaphthyl)aluminum or any combinations thereof.

It is recognized that these activators may bind directly to the supportsurface or be modified to allow them to be bound to a support surfacewhile still maintaining their compatability with the polymerizationsystem. Such tethering agents may be derived from groups that arereactive with surface hydroxyl species. Non-limiting examples ofreactive functional groups that can be used to create tethers includealuminum halides, aluminum hydrides, aluminum alkyls, aluminum aryls,sluminum alkoxides, electrophilic silicon reagents, alkoxy silanes,amino silanes, boranes.

Aluminoxanes can be described as oligomeric aluminum compounds having—Al(R)—O— subunits, where R is an alkyl group. Examples of aluminoxanesinclude, but are not limited to, methylaluminoxane (“MAO”), modifiedmethylaluminoxane (“MMAO”), ethylaluminoxane, isobutylaluminoxane, or acombination thereof. Aluminoxanes can be produced by the hydrolysis ofthe respective trialkylaluminum compound. MMAO can be produced by thehydrolysis of trimethylaluminum and a higher trialkylaluminum, such astriisobutylaluminum. MMAOs are generally more soluble in aliphaticsolvents and more stable during storage. There are a variety of methodsfor preparing aluminoxane and modified aluminoxanes.

In one or more examples, a visually clear MAO can be used. For example,a cloudy or gelled aluminoxane can be filtered to produce a clearaluminoxane or clear aluminoxane can be decanted from a cloudyaluminoxane solution. In another example, a cloudy and/or gelledaluminoxane can be used. Another aluminoxane can include a modifiedmethyl aluminoxane (“MMAO”) type 3A (commercially available from AkzoChemicals, Inc. under the trade name Modified Methylaluminoxane type 3A,discussed and described in U.S. Pat. No. 5,041,584). A suitable sourceof MAO can be a solution having from about 1 wt. % to about a 50 wt. %MAO, for example. Commercially available MAO solutions can include the10 wt. % and 30 wt. % MAO solutions available from AlbemarleCorporation, of Baton Rouge, La.

As noted above, one or more organo-aluminum compounds such as one ormore alkylaluminum compounds can be used in conjunction with thealuminoxanes. For example, alkylaluminum species that may be used arediethylaluminum ethoxide, diethylaluminum chloride, and/ordiisobutylaluminum hydride. Examples of trialkylaluminum compoundsinclude, but are not limited to, trimethylaluminum, triethylaluminum(“TEAL”), triisobutylaluminum (“TiBAl”), tri-n-hexylaluminum,tri-n-octylaluminum, tripropylaluminum, tributylaluminum, and the like.

Continuity Additive/Static Control Agents

In gas-phase polyethylene production processes, as disclosed herein, itmay be desirable to additionally use one or more static control agentsto aid in regulating static levels in the reactor. As used herein, astatic control agent is a chemical composition which, when introducedinto a fluidized bed reactor, may influence or drive the static charge(negatively, positively, or to zero) in the fluidized bed. The specificstatic control agent used may depend upon the nature of the staticcharge, and the choice of static control agent may vary dependent uponthe polymer being produced and the single site catalyst compounds beingused.

Control agents such as aluminum stearate may be employed. The staticcontrol agent used may be selected for its ability to receive the staticcharge in the fluidized bed without adversely affecting productivity.Other suitable static control agents may also include aluminumdistearate, ethoxlated amines, and anti-static compositions such asthose provided by Innospec Inc. under the trade name OCTASTAT. Forexample, OCTASTAT 2000 is a mixture of a polysulfone copolymer, apolymeric polyamine, and oil-soluble sulfonic acid.

Any of the aforementioned control agents, as well as those described in,for example, WO 01/44322, listed under the heading Carboxylate MetalSalt and including those chemicals and compositions listed as antistaticagents may be employed either alone or in combination as a controlagent. For example, the carboxylate metal salt may be combined with anamine containing control agent (e.g., a carboxylate metal salt with anyfamily member belonging to the KEMAMINE® (available from CromptonCorporation) or ATMER® (available from ICI Americas Inc.) family ofproducts).

Other useful continuity additives include ethyleneimine additives usefulin examples disclosed herein may include polyethyleneimines having thefollowing general formula:

—(CH₂—CH₂—NH)_(n)—

in which n may be from about 10 to about 10,000. The polyethyleneiminesmay be linear, branched, or hyperbranched (e.g., forming dendritic orarborescent polymer structures). They can be a homopolymer or copolymerof ethyleneimine or mixtures thereof (referred to aspolyethyleneimine(s) hereafter). Although linear polymers represented bythe chemical formula —[CH₂—CH₂—NH]— may be used as thepolyethyleneimine, materials having primary, secondary, and tertiarybranches can also be used. Commercial polyethyleneimine can be acompound having branches of the ethyleneimine polymer. Suitablepolyethyleneimines are commercially available from BASF Corporationunder the trade name Lupasol. These compounds can be prepared as a widerange of molecular weights and product activities. Examples ofcommercial polyethyleneimines sold by BASF suitable for use in thepresent invention include, but are not limited to, Lupasol FG andLupasol WF. Another useful continuity additive can include a mixture ofaluminum distearate and an ethoxylated amine-type compound, e.g.,IRGASTAT AS-990, available from Huntsman (formerly Ciba SpecialtyChemicals). The mixture of aluminum distearate and ethoxylated aminetype compound can be slurried in mineral oil e.g., Hydrobrite 380. Forexample, the mixture of aluminum distearate and an ethoxylated aminetype compound can be slurried in mineral oil to have total slurryconcentration of ranging from about 5 wt. % to about 50 wt. % or about10 wt. % to about 40 wt. %, or about 15 wt. % to about 30 wt. %.

The continuity additive(s) or static control agent(s) may be added tothe reactor in an amount ranging from 0.05 to 200 ppm, based on theweight of all feeds to the reactor, excluding recycle. In some examples,the continuity additive may be added in an amount ranging from 2 to 100ppm, or in an amount ranging from 4 to 50 ppm.

Polymerization Process

The catalyst system can be used to polymerize one or more olefins toprovide one or more polymer products therefrom. Any suitablepolymerization process can be used, including, but not limited to, highpressure, solution, slurry, and/or gas phase polymerization processes.

The terms “polyethylene” and “polyethylene copolymer” refer to a polymerhaving at least 50 wt. % ethylene-derived units. In various examples,the polyethylene can have at least 70 wt. % ethylene-derived units, atleast 80 wt. % ethylene-derived units, at least 90 wt. %ethylene-derived units, at least 95 wt. % ethylene-derived units, or 100wt. % ethylene-derived units. The polyethylene can, thus, be ahomopolymer or a copolymer, including a terpolymer, having one or moreother monomeric units. As described herein, a polyethylene can include,for example, at least one or more other olefins or comonomers. Suitablecomonomers can contain 3 to 16 carbon atoms, from 3 to 12 carbon atoms,from 4 to 10 carbon atoms, and from 4 to 8 carbon atoms. Examples ofcomonomers include, but are not limited to, propylene, 1-butene,1-pentene, 1-hexene, 1-heptene, 1-octene, 4-methylpent-l-ene, 1-decene,1-dodecene, 1-hexadecene, and the like. Additionally, small amounts ofdiene monomers, such as 1,7-octadiene may be added to the polymerizationto adjust polymer properties.

The reactor temperature of a fluid bed in a gas phase polymerizationprocess can be greater than about 30° C., about 40° C., about 50° C.,about 90° C., about 100° C., about 110° C., about 120° C., about 150°C., or higher. In general, the reactor temperature is operated at thehighest feasible temperature taking into account the sinteringtemperature of the polymer product within the reactor. Preferred reactortemperatures are between 70 and 95° C. More preferred reactortemperatures are between 75 and 90° C. Thus, the upper temperature limitin one example is the melting temperature of the polyethylene copolymerproduced in the reactor. However, higher temperatures may result innarrower MWDs, which can be improved by the addition of the MCN, orother, co-catalysts, as described herein.

Hydrogen gas can be used in olefin polymerization to control the finalproperties of the polyolefin. Using certain catalyst systems, increasingconcentrations (partial pressures) of hydrogen can increase the flowindex (FI) of the polyethylene copolymer generated. The flow index canthus be influenced by the hydrogen concentration. The amount of hydrogenin the polymerization can be expressed as a mole ratio relative to thetotal polymerizable monomer, for example, ethylene, or a blend ofethylene and hexene or propylene.

The amount of hydrogen used in the polymerization process can be anamount necessary to achieve the desired flow index of the finalpolyolefin resin. For example, the mole ratio of hydrogen to totalmonomer (H₂:monomer) can be greater than about 0.0001, greater thanabout 0.0005, or greater than about 0.001. Further, the mole ratio ofhydrogen to total monomer (H₂:monomer) can be less than about 10, lessthan about 5, less than about 3, and less than about 0.10. A desirablerange for the mole ratio of hydrogen to monomer can include anycombination of any upper mole ratio limit with any lower mole ratiolimit described herein. Expressed another way, the amount of hydrogen inthe reactor at any time can range to up to about 5,000 ppm, up to about4,000 ppm in another example, up to about 3,000 ppm, or between about 50ppm and 5,000 ppm, or between about 50 ppm and 2,000 ppm in anotherexample. The amount of hydrogen in the reactor can range from a low ofabout 1 ppm, about 50 ppm, or about 100 ppm to a high of about 400 ppm,about 800 ppm, about 1,000 ppm, about 1,500 ppm, or about 2,000 ppm.Further, the ratio of hydrogen to total monomer (H₂:monomer) can beabout 0.00001:1 to about 2:1, about 0.005:1 to about 1.5:1, or about0.0001:1 to about 1:1. The one or more reactor pressures in a gas phaseprocess (either single stage or two or more stages) can vary from 690kPa (100 psig) to 3,448 kPa (500 psig), in the range from 1,379 kPa (200psig) to 2,759 kPa (400 psig), or in the range from 1,724 kPa (250 psig)to 2,414 kPa (350 psig).

The gas phase reactor can be capable of producing from about 10 kg ofpolymer per hour (25 lbs/hr) to about 90,900 kg/hr (200,000 lbs/hr), orgreater, and greater than about 455 kg/hr (1,000 lbs/hr), greater thanabout 4,540 kg/hr (10,000 lbs/hr), greater than about 11,300 kg/hr(25,000 lbs/hr), greater than about 15,900 kg/hr (35,000 lbs/hr), andgreater than about 22,700 kg/hr (50,000 lbs/hr), and from about 29,000kg/hr (65,000 lbs/hr) to about 45,500 kg/hr (100,000 lbs/hr).

As noted, a slurry polymerization process can also be used in examples.A slurry polymerization process generally uses pressures in the range offrom about 101 kPa (1 atmosphere) to about 5,070 kPa (50 atmospheres) orgreater, and temperatures in the range of from about 0° C. to about 120°C., and more particularly from about 30° C. to about 100° C. In a slurrypolymerization, a suspension of solid, particulate polymer can be formedin a liquid polymerization diluent medium to which ethylene, comonomers,and hydrogen along with catalyst can be added. The suspension includingdiluent can be intermittently or continuously removed from the reactorwhere the volatile components are separated from the polymer andrecycled, optionally after a distillation, to the reactor. The liquiddiluent employed in the polymerization medium can be an alkane havingfrom 3 to 7 carbon atoms, such as, for example, a branched alkane. Themedium employed should be liquid under the conditions of polymerizationand relatively inert. When a propane medium is used the process shouldbe operated above the reaction diluent critical temperature andpressure. In one example, a hexane, isopentane, or isobutane medium canbe employed. The slurry can be circulated in a continuous loop system.

The product polyethylene can have a melt index ratio (MIR or I₂₁/I₂)ranging from about 5 to about 300, or from about 10 to less than about150, or, in many examples, from about 15 to about 50. Flow index (FI,HLMI, or I₂₁ can be measured in accordance with ASTM D1238 (190° C.,21.6 kg). The melt index (MI, I₂) can be measured in accordance withASTM D1238 (at 190° C., 2.16 kg weight).

Density can be determined in accordance with ASTM D-792. Density isexpressed as grams per cubic centimeter (g/cm³) unless otherwise noted.The polyethylene can have a density ranging from a low of about 0.89g/cm³, about 0.90 g/cm³, or about 0.91 g/cm³ to a high of about 0.95g/cm³, about 0.96 g/cm³, or about 0.97 g/cm³. The polyethylene can havea bulk density, measured in accordance with ASTM D1895 method B, of fromabout 0.25 g/cm³ to about 0.5 g/cm³. For example, the bulk density ofthe polyethylene can range from a low of about 0.30 g/cm³, about 0.32g/cm³, or about 0.33 g/cm³ to a high of about 0.40 g/cm³, about 0.44g/cm³, or about 0.48 g/cm³.

Controlling Product Properties

The properties of the product polymer may be controlled by adjusting thetiming, temperature, concentrations, and sequence of the mixing of thesolution, the slurry and any optional added materials (nucleatingagents, catalyst compounds, activators, etc.) described above. Thecontrol may be achieved by measuring a sample of the polyethylenecopolymer to obtain an initial product property; and changing a processparameter to obtain a second product property, based, at least in part,on the initial product property.

The MWD, composition distribution, melt index, relative amount ofpolymer produced by each catalyst, and other properties of the polymerproduced may also be changed by manipulating process parameters. Anynumber of process parameters may be adjusted, including manipulatinghydrogen concentration in the polymerization system, changing the amountof a catalyst in the polymerization system, changing the amount of asecond catalyst in the polymerization system. Other process parametersthat can be adjusted include changing the relative ratio of the catalystin the polymerization process, and optionally adjusting their individualfeed rates to maintain a steady or constant resin production rate. Theconcentrations of reactants in the reactor can be adjusted by changingthe amount of liquid or gas that is withdrawn or purged from theprocess, changing the amount and/or composition of a recovered liquidand/or recovered gas returned to the polymerization process, wherein therecovered liquid or recovered gas can be recovered from polymerdischarged from the polymerization process. Further concentrationparameters that can be adjusted include changing the polymerizationtemperature, changing the ethylene partial pressure in thepolymerization process, changing the ethylene to comonomer ratio in thepolymerization process, changing the activator to transition metal ratioin the activation sequence. Time dependent parameters may be adjusted,such as changing the relative feed rates of the slurry or solution,changing the mixing time, the temperature and or degree of mixing of theslurry and the solution in-line, adding different types of activatorcompounds to the polymerization process, and adding oxygen orfluorobenzene or other catalyst poison to the polymerization process.Any combinations of these adjustments may be used to control theproperties of the final polymer product.

In one example, the composition distribution of the polymer product ismeasured at regular intervals and one of the above process parameters,such as temperature, catalyst compound feed rate, the ratio of comonomerto monomer, the monomer partial pressure, and or hydrogen concentration,is altered to bring the composition to the desired level, if necessary.The composition distribution may be performed by temperature risingelution fractionation (TREF), or similar techniques.

The polyethylene can be suitable for such articles as films, fibers,nonwoven and/or woven fabrics, extruded articles, and/or moldedarticles. Examples of films include blown or cast films formed bycoextrusion or by lamination useful as shrink film, cling film, stretchfilm, sealing films, oriented films, snack packaging, heavy duty bags,grocery sacks, baked and frozen food packaging, medical packaging,industrial liners, membranes, etc. in food-contact and non-food contactapplications, agricultural films and sheets. Examples of fibers includemelt spinning, solution spinning and melt blown fiber operations for usein woven or non-woven form to make filters, diaper fabrics, hygieneproducts, medical garments, geotextiles, etc. Examples of extrudedarticles include tubing, medical tubing, wire and cable coatings, pipe,geomembranes, and pond liners. Examples of molded articles includesingle and multi-layered constructions in the form of bottles, tanks,large hollow articles, rigid food containers and toys, etc.

EXAMPLES

To provide a better understanding of the foregoing discussion, thefollowing non-limiting examples are provided. All parts, proportions,and percentages are by weight unless otherwise indicated.

General Experimental Procedures

All manipulations were performed in an N₂ purged glovebox or usingstandard Schlenk techniques. All anhydrous solvents were purchased fromSigma-Aldrich and were degassed and dried over calcined Al₂O₃ beads ormolecular sieves prior to use. Deuterated solvents were purchased fromCambridge Isotope Laboratories and were degassed and dried over aluminabeads or molecular sieves prior to use. Reagents used were purchasedfrom various commercial suppliers or made by literature methods. ¹H NMRmeasurements were recorded on a 250MHz, 400MHz or a 500MHz Brukerspectrometer.

Catalyst Preparations

Synthesis of (n-propylcyclopentadienyl)zirconiumtrichloride

Bis(n-propylcyclopentadienyl)zirconiumdichloride (14.83 g) was heated to130° C. with stirring forming a viscous liquid. ZrCl₄ (9.18 g) wasadded. The temperature was reduced to 125° C. The reaction was heatedunder vacuum for 6 h. during which time a yellow crystalline solidsublimed out of the reaction mixture and collected on the walls of theflask. Yield=21.7 g. Based on the structure the complex is present asthe tetramer, with the crystal structure shown in FIG. 1.

Synthesis of (n-propylcyclopentadienyl)zirconiumtrichloride

Bis(n-propylcyclopentadienyl)zirconiumdichloride (22.7 g) was heated to130° C. with stirring forming a viscous liquid. ZrCl₄ (14.1 g) wasadded. The temperature was reduced to 125° C. The reaction was heatedunder vacuum for 6 h. during which time a yellow crystalline solidsublimed out of the reaction mixture and collected on the walls of theflask. Yield=21.7 g. The remaining material was again heated to 125° C.under vacuum for 6 h. resulting in an additional yield of 10.0 g. Totalyield=31.7 g.

Synthesis of n-propylcyclopentadienyl)zirconiumtrichloride(dimethoxyethane)

Bis(n-propylcyclopentadienyl)zirconiumdichloride (13.86 g) and ZrCl₄(8.68 g) were added together as solids at 120° C. and heated undervacuum for 7 h. during which time a yellow crystalline solid sublimedout of the reaction mixture and collected on the walls of the flask.Yield=19.08 g. The solid was dissolved in toluene (ca. 70 mL) and DME(ca. 25 mL) was added. This was heated to 80° C. forming a clearsolution which formed a colorless crystalline solid upon cooling to roomtemperature. A solution of toluene and pentane (ca. 50 mL; 1 to 1 ratio)was added and the mixture was cooled to −22° C. The resulting solid wasisolated by filtration, washed with pentane (2×60 mL) and dried undervacuum. Yield=23.2 g (85% yield based onbis(n-propylcyclopentadienyl)zirconiumdichloride)

Synthesis of (n-propylcyclopentadienyl)zirconiumtrichloride(dimethoxyethane)

Bis(n-propylcyclopentadienyl)zirconiumdichloride (13.25 g; 35.3 mmol)and ZrCl₄ (8.20 g; 35.2 mmol) were added together as solids and heatedto 135° C. for 30 min resulting in a thick liquid. The reaction washeated under vacuum for 7.5 h. during which time a yellow crystallinesolid sublimed out of the reaction mixture and collected on the walls ofthe flask. Yield=17.2 g. All the solid was dissolved in toluene (ca. 80mL) and DME (ca 30 mL) added. The flask was heated to about 90° C. todissolve all the solids and an aliquot was removed, dried down and the¹H NMR in C₆D₆ was taken which showed(n-propylcyclopentadienyl)zirconiumtrichloride withbis(n-propylcyclopentadienyl)zirconiumdichloride (ca. 3%) and an almostbarely detectable DME peak associated with ZrCl₄. Upon cooling acolorless crystalline material precipitated, pentane (ca. 70 mL) wasadded with stirring. The solid was isolated by filtration, washed withpentane (ca. 50 mL) and dried under vacuum. Yield=19.25 g. The ¹H NMR inC₆D₆ is shown in FIG. 2 and showed no detectable impurities.

Synthesis of (n-propylcyclopentadienyl)(1-methylindenyl)zirconiumdichloride

1-methylindenyllithium (8.13 g, 60 mmol)) was dissolved in 300 mLdiethylether and solid(n-propylcyclopentadienyl)zirconiumtrichloride(dimethoxyethane) (23.6 g;60 mmol) was added rapidly and an additional 100 mL diethylether wasadded. After stirring overnight the diethylether was removed undervacuum, and 300 mL toluene was added. The flask was heated to 60° C. andthe solution was isolated by filtration. The volume was concentrated toabout 100 mL and heated to 95° C. to dissolve all solids, upon coolingyellow crystalline solid formed. Hexanes (150 mL) was added, the solidwas broken up with a spatula, isolated by filtration and washed withhexanes (100 mL) and dried under vacuum at 60° C. to give 19.6 g. Asecond crop of product was obtained by concentration and cooling of thecombined supernatant and washings. It was isolated, washed and dried asdescribed above. Total yield=21.1 g. The solids were dissolved in CH₂Cl₂and an aliquot was removed, dried down and redissolved in C₆D₆ to obtainthe ¹H NMR, which is shown in FIG. 3.

Synthesis of (1,3-butyl-methyl-cyclopentadienyl)zirconiumtrichloride

Bis(1,3-butyl-methyl-cyclopentadienyl) zirconiumdichloride (1.6 g) wasput into a scintillation vial and heat was turned on. As the temperaturereached 75° C. the ECl₂ began to melt and ZrCl₄ (0.88 g) was added. Theheat was raised to 130° C. forming a brown liquid. After 30 min a dropwas removed, dissolved in DME and dried down. The ¹H NMR in C₆D₆ showeda 5:1 ratio of (1,3-butyl-methyl-cyclopentadienyl)zirconiumtrichlorideto bis(1,3-butyl-methyl-cyclopentadienyl) zirconiumdiichloride with asmall amount of some other product. After heating an additional hour at130° C. a drop was analyzed as described above and showed a 5.7 to 1ratio of (1,3-butyl-methyl-cyclopentadienyl)zirconiumtrichloride tobis(1,3-butyl-methyl-cyclopentadienyl) zirconiumdichloride.

Using a sublimation apparatus, bis(1,3-butyl-methyl-cyclopentadienyl)zirconiumdichloride (10.35 g; 23.92 mmol) was heated to about 100° C. toform a liquid and ZrCl₄ (5.62 g; 24.12 mmol) was added. The reaction washeated at 130° C. for 1.5 h and a small sample was removed. The ¹H NMRof this sample was obtained in C₆D₆ after treatment with DME asdescribed above and showed a 5.7 to 1 ratio of(1,3-butyl-methyl-cyclopentadienyl) zirconiumtrichloride tobis(1,3-butyl-methyl-cyclopentadienyl) zirconiumdichloride. The reactionwas heated at 130° C. for 5 h. under vacuum during this time it wasnoticed that the yellow oil that was subliming/distilling out of thereaction mixture was running back down into the reaction mixture. Fromthe sublimation tube, 2.2 g of a yellow oil was obtained. The ¹H NMR ofthis sample, was obtained in C₆D₆ after treatment with DME, and showedmono with a trace of the bis compound.

Synthesis of (1,3-butyl-methyl-cyclopentadienyl)zirconiumtrichloride

Bis(1,3-butyl-methyl-cyclopentadienyl)zirconiumdichloride (11.12 g; 25.7mmol) was added to a 50 mL round bottom flask and heated about 100° C.which caused it to melt. Solid ZrCl₄ (6.01 g; 25.7 mmol) was added. Theflask was fitted to an adapter and the adapter was attached to aroto-vap bump trap and placed under vacuum. Light yellow oil collectedin the trap. It was dissolved in toluene and an aliquot was removed (ca.1 mL) treated with DME (ca. 0.5 mL) and dried down to a solid. The ¹HNMR in C₆D₆ showed the presence of(1,3-butyl-methyl-cyclopentadienyl)zirconiumtrichloride as the DMEadduct (98%) andbis(1,3-butyl-methyl-cyclopentadienyl)zirconiumdichloride (2%). Thetoluene was removed under vacuum and the oil re-dissolved in DME (ca. 30mL). An additional 2 g of(1,3-butyl-methyl-cyclopentadienyl)zirconiumtrichloride was dissolved inDME and added to the solution along with toluene (ca. 30 mL). Thesolvent was removed under vacuum leaving a light yellow oil. Pentane(ca. 50 mL) was added and the suspension was stirred vigorously. Aftersitting overnight the oil solidified/crystallized out. The solvent wasdecanted, the solid broken up, stirred with pentane (ca. 60 mL),isolated by filtration, washed with pentane (2×30 mL) and dried undervacuum to give a colorless solid. Yield=14.1 g. The ¹H NMR shown in FIG.4 showed minimal impurities.

Synthesis of (n-Propylcyclopentadienyl)hafnium trichloride(dimethoxyethane)

bis(n-Propylcyclopentadienyl)hafniumdichloride [(nPrCp)₂HfCl₂] (25.1 g;54.1 mmol) was heated to 140° C. in a 100 mL round-bottom flask untilmelted. HfCl₄ (17.5 g; 54.6 mmol) was added as a solid powder. Themixture was heated at 140° C. for about 30 min forming a brown viscousliquid. The 100 mL round bottom flask was attached to a short pathdistillation apparatus which consisted of a glass tube (90° bend) thatwas attached to a Schlenk flask. A vacuum was pulled on the assemblythrough the stopcock of the Schlenk flask. The temp was raised to 160°C. Over about an hour most of the material distilled/sublimed into theSchlenk flask or remained in the glass tube. The solid material in theu-tube was scraped out and combined with the material in the Schlenkflask. To this solid was added toluene (ca. 50 mL) and dimethoxyethane(ca. 50 mL). This was heated to reflux forming a solution, additionaltoluene (ca. 50 mL) was added. Upon cooling colorless needles formed.Pentane (ca. 200 mL) was added causing further formation of solidprecipitate. The solid was isolated by filtration, washed with pentane(2×50 mL) and dried under vacuum. Yield=42.2 g; Cooling the combinedsupernatant and washings resulted an additional 2.6 g of product thatwas isolated. Total yield=44.8 g (86%).

The reaction was repeated in a similar manner using 11.92 g (25.7 mmol)of (nPrCp)₂HfCl₂ and 8.3 g (25.9 mmol) of HfCl₄. The total yield of thisreaction was 22.4 g (90.4%). The NMR for this compound is shown in FIG.5.

Synthesis of a mixed ligand compound

(N-propylcyclopentadienyl)zirconiumtrichloride (dimethoxyethane) (2.25g; 5.7 mmol) was slurried in ether (50 mL) and benzylmagnesiumchloride(1.0 M solution in ether, 19.0 mL; 19 mmol) was added. After stirring 3h at room temperature the ether was removed under vacuum and tolueneadded (30 mL) forming a slurry to which 1,4-dioxane (5 mL) was addedcausing more precipitation to occur. The solution was isolated byfiltration then dried under vacuum for 2 hours at 60° C. Yield=2.4 g.The oil was dissolved in 10. 0 mL toluene to give a solution of(n-propylcyclopentadienyl)zirconiumtribenzyl with an approximateconcentration of 0.194 g/mL. To 7.54g of the(n-propylcyclopentadienyl)zirconiumtribenzyl solution (3.59 mmol of theZr compound) was added toluene (10 mL) and a toluene solution of thephosphine ligand (solution concentration of ligand=0.138 g/mL; 7.08 gsolution; 3.59 mmol of ligand). After stirring 1.5 h, the solvent wasremoved under vacuum and pentane was added to form a solution that wascooled at −35° C. overnight to give yellow/brown crystalline solid. Thesolid was isolated by decanting the supernatant and washing the solidwith cold pentane. The product was recrystallized from hot hexanes togive large yellow crystals. The NMR for this compound is shown in FIG.6. FIG. 7 is a crystal structure of this compound.

All numerical values are “about” or “approximately” the indicated value,and take into account experimental error and variations that would beexpected by a person having ordinary skill in the art. Further, variousterms have been defined above. To the extent a term used in a claim isnot defined above, it should be given the broadest definition persons inthe pertinent art have given that term as reflected in at least oneprinted publication or issued patent. All patents, test procedures, andother documents cited in this application are fully incorporated byreference to the extent such disclosure is not inconsistent with thisapplication and for all jurisdictions in which such incorporation ispermitted.

While the foregoing is directed to examples of the present invention,other and further examples of the invention can be devised withoutdeparting from the basic scope thereof, and the scope thereof isdetermined by the claims that follow.

1.-20. (canceled)
 21. A method of synthesizing a monocyclopentadienylcompound, comprising: melting a dicyclopentadienyl compound comprisingthe following structure:

wherein M is hafnium or zirconium; each R is independently an H, ahydrocarbyl group, a substituted hydrocarbyl group, a heteroatom group;and each X is a leaving group selected from a halogen or a heteroatomgroup; forming a reaction melt by adding a metal salt comprising thefollowing structure:

and depositing a monocyclopentadienyl compound from a vapor formed overthe reaction melt, wherein the monocyclopentadienyl compound comprisesthe following structure:


22. The method of claim 21, comprising continuously adding thedicyclopentadienyl compound and the metal salt to the reaction melt,while continuously depositing the monocyclopentadienyl compound from thevapor.
 23. The method of claim 21, wherein the dicyclopentadienylcompound comprises the following structure:


24. The method of claim 21, wherein the dicyclopentadienyl compoundcomprises the following structure: